This proposal requests salary support for the applicant under the ADAMHA Research Scientist Development Program, Level II. It would enable him to assume a full-time appointment at New York State Psychiatric Institute, Department of Psychophysiology. The research plan, covering five years, concentrates on studies of behavioral and biological functions which comprise an organism's time-keeping repertoire. The experiments are based on behavioral, psychophysical and neuro-anatomical methods for analyzing a set of short-interval and circadian timing mechanisms, and their interactions. Specific topics include: a) Temporal Anticipation in the Short-Interval and Circadian Ranges, using exteroceptively cued feeding schedules; b) Short-Interval Timing with Circadian Activity Rhythms, using the Time-Left psychophysical method for assessing changes in the speed of an internal clock; c) Behavioral Analysis of Luminance Detectability Rhythms, using a signal-detection paradigm to study circadian oscillations in visual threshold; and c) Retinal Photoreceptor Organization and Circadian Variation in Visual Sensitivity, using coordinated anatomical and behavioral methods to specify the relation of rod outer-segment mechanisms to oscillating detection performance. Additionally, the candidate proposes to develop interactions with clinical research staff of the institute whose interests relate to circadian timing processes in patient populations.